The invention concerns a device for ground copying for front attachments to harvesting machines, especially for self-propelled combine harvesters and forage choppers, in accordance with the features in the generic terms of claim 1.
Such devices for ground copying serve to adjust the front attachments to the unevenness of the ground, so that the crop can be harvested without loss even under these conditions. For this it is adequately known to fix the attachments to the harvesting machine so that they can swivel, so that on the one hand the so-called longitudinal movement of copying can be executed along the axis transverse to the direction of travel of the machine and on the other hand transverse copying can be effected along an axis pointing in the direction of travel. The cases for the application of such devices for ground copying extend to cutting and mowing machines of all types of construction and to gathering devices on the most varied types of harvesting machines. Therefore they have become so important, as all these attachments must have an appropriately wide working width because of the very high productive capacity of the present-day harvesting machines. In the state of the art a multitude of variant embodiments for this have already become known, which can be divided into two large categories.
The first category is described in EP 0 331 893 B1, in which the attachment is fixed on the front side of the harvesting machine so that it can tilt for the purpose of copying longitudinally and transversely. Two hydraulic cylinders arranged at a distance from each other and symmetrically about the central longitudinal axis of the harvesting machine support the attachment from below with a force such that is presses on the ground only with a residual weight and consequently with a slight pressure, in order to be able to follow the irregularities of the ground via skates, running wheels or its ground trough itself for longitudinal copying. For keeping to a set value for the ground pressure either by means of suitable sensors, the pressure in the hydraulic cylinders or the supporting force of the hydraulic cylinders on the chassis of the harvesting machine is monitored. In the event of a deviation from this set value the piston rods of the hydraulic cylinders are driven so far in or out until the set value again prevails, which is associated with a raising or lowering of the attachment. For transverse copying the attachment is equipped in its outer side regions with sprung elastic slide hoops, which detect the ground and via a potentiometer connected to them furnish a measure of the distance of the attachment from the ground. If the signals from both sides differ from each other, two further hydraulic cylinders have pressure applied to them, which are applied in a vertical direction between for example the feeder shaft of the combine harvester and the attachment, which tilt the attachment laterally until on both sides of the attachment the same distance is restored again.
Such devices for ground copying serve to adjust the front attachments to the unevenness of the ground, so that the crop can be harvested without loss even under these conditions. For this it is adequately known to fix the attachments to the harvesting machine so that they can swivel, so that on the one hand the so-called longitudinal movement of copying can be executed along the axis transverse to the direction of travel of the machine and on the other hand transverse copying can be effected along an axis pointing in the direction of travel. The cases for the application of such devices for ground copying extend to cutting and mowing machines of all types of construction and to gathering devices on the most varied types of harvesting machines. Therefore they have become so important, as all these attachments must have an appropriately wide working width because of the very high productive capacity of the present-day harvesting machines. In the state of the art a multitude of variant embodiments for this have already become known, which can be divided into two large categories.
As regards this device for ground copying, it can be criticized on the one hand since because of the constantly flowing hydraulic oil it reacts to a considerable degree much too sluggishly. On the other hand it delivers the control signal for longitudinal copying much too late. Furthermore there is a disadvantage that through ground detection under different weather conditions, through constantly changing leverage ratios and hysteresis phenomena in the lifting system and through the influence of markedly fluctuating dynamic forces, practically no reproducible set values for ground pressure can be realized. The consequence of this is that obstacles cannot be avoided and its operability is put into question even at moderate driving speeds.
The second category of devices for ground copying, one embodiment of which is described in EP 0 748 153 B1, works alongside the facility proposed in the first category via direct ground contact of the attachment now principally without this. For this, ultrasound sensors are fixed on both sides in the region of its sidewalls, which continuously measure the distance of the attachment from the ground and produce a corresponding output signal. In the driver""s cab of this harvester a control device is installed, which receives the output signals from the ultrasound sensors and in the event of a deviation from a prescribed set value for the distance it addresses a control valve in the hydraulic circuit of the hydraulic cylinder for raising and lowering the attachment. Since the hydraulic cylinder is arranged analogously to the solution described in the foregoing and is actuated likewise, this system operates just as sluggishly and imprecisely as regards adherence to the set value for the distance between the attachment and the ground. The ultrasound sensors present an additional disturbing factor, as they cannot distinguish between plants or stubble lying on the ground and the ground itself, so that under these conditions they deliver false distances. Because of their arrangement just above the ground, these errors are made especially noticeable. Furthermore, ultrasound sensors react to wind and humidity with a large scattering of the measured values. In addition they are relatively expensive to purchase, so that all these disadvantages taken together could be the reason that such a device for ground copying has not been accepted in practice.
Setting out from the negative experiences from the afore-described solution, a further device for ground copying has been published in EP 0 511 768 B1 and EP 0 936 475 A1, where the ultrasound sensors employed there are fixed far above the ground and in the side region of the attachments. With this it is achieved that only the measurement error for distance caused by stubble or plants lying on the ground is diminished somewhat as a percentage.
A further possibility for a device for ground copying be means of ultrasound sensors is described in EP 0 765 594 A1 with an example of a combine harvester cutter. There the ultrasound sensors measure continuously the distance to the sensor skids attached to the exterior of the cutter with the aid of a plate attached to them, in order to exclude the error from ground sensing. However this measure alone is not sufficient for well-functioning ground copying. Furthermore, the angle of incidence and emission to the plate varies constantly, so that distortions to the measurement of distance occur.
To be assessed analogously is the ground copying in accordance with DE 196 01 420 A1, where a prestressed sliding element of narrow spring steel senses the ground and transmits its movement in consequence of ground irregularities to a signal transmission element. This is formed as a parallelogram of rods, to which a plate is attached, which in contrast to the previously described plate on the sensor skid executes approximately parallel movements. This is irradiated by a wave sensor and reflects its radiation. From this the wave sensor determines a measure for the change in position of the sliding element, which is in a directly proportional ratio to the distance of the attachment from the ground. The measure thus determined with a somewhat greater accuracy, is however used finally also only for driving a control valve in the hydraulic circuit for the hydraulic cylinder for raising and lowering the front attachment, so that all the previously mentioned disadvantages cannot be removed even with this ground copying. An additional deficiency is caused be the narrow sliding elements in the presence of longitudinal grooves in the ground, as they then indicate a false distance.
Therefore the objective of the invention is to create a device for ground copying for front attachments to harvesting machines, which reacts rapidly to irregularities in the ground, even at higher driving speeds, which adheres with greater precision to the distance of the attachment from the ground, which is prescribed as the set value, and which is manufacturable economically.
This objective is solved according to the invention by the features of the 1st claim, in which the features are listed in the subclaims, which further develop this solution in an advantageous manner.
Through the attachment of the feeder device to the harvesting machine by means of powerful hydraulic cylinders so that its height can be altered, it is possible to tilt this, together with the attachment fixed to the front, through a relatively large range, which is used superficially for adjusting the starting position of the attachment for proper use and raising it to a transport position. Because of the size of this hydraulic cylinder and the flow of large quantities of hydraulic oil associated with it this movement takes quite a long time. Therefore for the purpose of longitudinal copying on the ground, the attachment is fixed to the feeder device so that it can tilt on an axle aligned transversely to the direction of travel of travel of the harvesting machine, so that it can move relative to the fixed feeder device about a defined angle of tilt. For monitoring the defined range for the angle of tilt, a sensor is arranged in a fixed position on the feeder device, which is in contact with the attachment. For the enforced movement of the attachment within the defined range, according to the invention between it and the feeder device a relatively smaller, and hence fast reacting hydraulic working cylinder, is envisaged.
On the attachment there is at feast one further sensor, which constantly measures the distance of the attachment from the ground. Both sensors furnish electrical signals, which are passed on to a controller, which can influence the hydraulic system of the hydraulic cylinder beneath feeder device and that of the hydraulic working cylinder between the feeder device and the front attachment.
A more expedient embodiment of the device for ground copying in accordance with the invention consists in that the distance of the attachment from the ground is determined by feelers sliding along the ground and which are moveable as regards height relative to the attachment, which transmit their height movement proportionally to so-called angular sensors for producing an appropriate output voltage. In the case of the use of a cutter as an attachment, it is suggested to use as a feeler just the stem divider located in the region of the sidewalls plainly front of the cutter bar.
In a further advantageous embodiment of the invention it has proved its worth, to suspend the attachment on the feeder device so as to be capable additionally of tilting about an axis pointing in the direction of travel of the harvesting machine for the purpose of transverse copying. A further hydraulic cylinder arranged accordingly between the feeder device and the attachment is likewise connected to the controller, which for its operation utilizes the signals from the sensors for measuring the distance.
The method of functioning of the device for ground copying begins thus, in that a preselection of the mode of operation of the attachment is made through an operating element located in the driver""s cab of the harvesting machine, in which the pushbutton for xe2x80x9cground copyingxe2x80x9d is pressed. Thus the controller designed as a software controller for executing the necessary control and computing operations for ground copying is activated. Then a set-value transmitter is adjusted to the desired set distance of the attachment from the ground, which is conveyed to the controller via its input lead. Also the left and right hand sensors in the stem divider, which continually determine the actual distance of the attachment from the ground, deliver their values and the sensor for monitoring the defined range for the angle of tilt likewise delivers its value to the controller via separate input leads.
As long as the front attachment is in the transport position or is on the way to its starting position for field use, the two actual distances are greater than the set-value for distance and the controller lowers the feeder device together with the attachment in the direction of the ground. Previously or simultaneously via the hydraulic working cylinder it sets the attachment to the mean value of the defined range for the angle of tilt, the attainment of which is signaled by the sensor between the feeder device and the attachment. Incidentally, so that the attachment when longitudinal copying can follow all ordinarily large bumps and dips in the ground within the defined range for the angle of tilt, it has proved expedient to permit for this about a 10-degree range of freedom. The starting position of the attachment for field use is then reached, if the two actual distances or the average value for actual distance calculated by the controller agree with the set-value for distance, and hydraulic cylinders thereupon stop the lowering movement of the feeder device.
The longitudinal copying in field use over above averagely large bumps and dips in the ground is executed by the hydraulic working cylinder alone, as long as the angle of tilt lies within its defined range. For this the controller compares the mean actual distance of the attachment from the ground and accordingly controls magnitude of the deviation of the hydraulic working cylinder to a length for immediate readjustment to the set distance. If the attachment encounters above averagely large bumps and depressions in the ground, the angle of tilt attains the upper or lower limit of the defined range. This is reported by the sensor for monitoring the angle of tilt to the controller, which thereupon raises or lowers the feeder device via its hydraulic cylinders so far, until the angle of tilt is again within its defined range. At the same time they hydraulic working cylinder likewise via the control signals from the controller takes care of adherence to the set-value for distance.
In a further preferred variant embodiment of the invention, the longitudinal copying according to the invention is advantageously combined with simultaneous transverse copying, in which the controller transmits to the hydraulic cylinder a control signal from the difference in the actual distance, which tilts the attachment about an axis which points along the direction of travel of the harvesting machine.
To sum up, the advantages of the invention are that with it very rapid ground copying has become possible for the front attachment of a harvesting machine, which shows itself particularly at high traveling speeds of the harvesting machine. The sensors which measure the distance of the attachment from the ground in the embodiment of mechanical feelers in conjunction with angular sensors delivering electrical signals furnish the most precise values, so that the attachment can follow the ground contour exactly. Finally, for this device for ground copying only simple components, which are already present on harvesting machines, are necessary so that their costs of manufacture are kept within limits.